Cost, affordability and cost-effectiveness of strategies to control tuberculosis in countries with high HIV prevalence

Abstract

Background: The HIV epidemic has caused a dramatic increase in tuberculosis (TB) in East and southern Africa. Several strategies have the potential to reduce the burden of TB in high HIV prevalence settings, and cost and cost-effectiveness analyses can help to prioritize them when budget constraints exist. However, published cost and cost-effectiveness studies are limited.

Methods: Our objective was to compare the cost, affordability and cost-effectiveness of seven strategies for reducing the burden of TB in countries with high HIV prevalence. A compartmental difference equation model of TB and HIV and recent cost data were used to assess the costs (year 2003 USD prices) and effects (TB cases averted, deaths averted, DALYs gained) of these strategies in Kenya during the period 2004-2023.

Results: The three lowest cost and most cost-effective strategies were improving TB cure rates, improving TB case detection rates, and improving both together. The incremental cost of combined improvements to case detection and cure was below USD 15 million per year (7.5% of year 2000 government health expenditure); the mean cost per DALY gained of these three strategies ranged from USD 18 to USD 34. Antiretroviral therapy (ART) had the highest incremental costs, which by 2007 could be as large as total government health expenditures in year 2000. ART could also gain more DALYs than the other strategies, at a cost per DALY gained of around USD 260 to USD 530. Both the costs and effects of treatment for latent tuberculosis infection (TLTI) for HIV+ individuals were low; the cost per DALY gained ranged from about USD 85 to USD 370. Averting one HIV infection for less than USD 250 would be as cost-effective as improving TB case detection and cure rates to WHO target levels.

Conclusion: To reduce the burden of TB in high HIV prevalence settings, the immediate goal should be to increase TB case detection rates and, to the extent possible, improve TB cure rates, preferably in combination. Realising the full potential of ART will require substantial new funding and strengthening of health system capacity so that increased funding can be used effectively.

Figure 1

Trends in HIV prevalence and TB notifications in Kisumu District, Kenya Source: personal communication, John Mansoer (National TB programme, Kenya) and Laurence Mareum (Centers for Disease Control, Kenya).

Figure 2

Outline of the tuberculosis (TB) sub-model. In the full model (see Methods, and supplementary material of [10]), active TB may be infectious or non-infectious, with movement allowed from active non-infectious disease to active infectious disease. An identical sub-model, with different parameter values, describes those with HIV. Death can occur in any state, but death rates are higher for patients with active disease.

Figure 3

Numbers receiving treatment for different strategies: (a) number of TB patients treated; (b) number of person years of AIDS-related opportunistic infection treatment and palliative care (not including ART); (c) number of person years of TLTI; (d) number of person years of ART. CDR = Case detection rate. CR = Cure rate. 6 m = 6 months. ART 50%, ART 20% and ART 5% mean ART with a 50%, 20% and 5% drop out rate, respectively. ART TB is ART for TB patients only, at a dropout rate of 20%. (k) means thousands.

Figure 4

Incremental costs compared to baseline scenario for each strategy. Black line represents estimated total government health expenditure in Kenya in the year 2000. See Figure 3 text for label definitions.

Figure 5

Disability adjusted life years (DALYs) gained by each strategy. See Figure 3 text for label definitions.

Figure 6

Cost-effectiveness of each strategy, with 95% confidence intervals. See Figure 3 text for label definitions.

Figure 7

Effect of each strategy on TB incidence and TB deaths: (a) TB incidence per 100,000 population; (b) TB deaths per 100,000 population. See Figure 3 text for label definitions.